Current trends in urban heat island mitigation research: Observations based on a comprehensive research repository

Scientific research on the mitigation of the urban heat island (UHI) phenomenon has been growing, reflecting a new awareness from scientists, planning authorities, and governmental bodies to the effects of urban design and planning on UHI summer intensity. This article aims at analysing current research trends on UHI mitigation through a comprehensive survey of scientific articles published on UHI mitigation between the years 2009-2013. The survey produced a repository of 411 papers and identified 11 discrete mitigation measures that are commonly studied today. In addition, the geographical distribution of research and its reliance on different methodologies and on external funding was also reviewed. Analysis showed a clear inclination of researchers towards a small set of mitigation measures (shade trees, cool building envelopes, ground vegetation, and green roofs). Research on mitigation measures is mainly conducted in regions of subtropical climate and large developed urban areas in East Asia, North America, and the European part of the Mediterranean Sea. Studies comparing the effect of several mitigation measures are less common than studies dedicated to a single mitigation measure, which may become less beneficial for policy makers, who usually have to decide which type of measures needed the most urgent type of promotion.